Patent Application
20080081237
A description will be made of a power generation system according to an embodiment of the present invention.
According to this embodiment, there is provided a power generation system including: a first power generation device and a second power generation device for generating power by using a fuel supply device and a fuel; a fuel path connecting the fuel supply device to the first power generation device and second power generation device, for supplying the fuel; and a fuel control device including a normally closed valve provided in the fuel path between the second power generation device and the fuel supply device, in which the fuel path between the fuel supply device and the normally closed valve is connected to the first power generation device, and the normally closed valve is structured as a valve opened by an output of the first power generation device.
According to this embodiment as described above, in order to control fuel supply to the second power generation device, the normally closed valve is structured so as to be opened by the output of the first power generation device, thereby eliminating a need for preparing a new power source device for actuation in a case of supplying power to an electronic equipment or the like.
Further, when an output of the first power generation device is extremely reduced in an abnormal state, the normally closed valve is automatically closed, whereby the fuel supply to the second power generation device can be stopped.
As a result, the power generation system with high stability can be achieved employing the small number of components. Further, there can be realized a power generation device which is compatible with the small electronic equipments and which can stably generate power.
Note that, the power generation system according to this embodiment is not limited to the above-mentioned structure. Another embodiment can be realized in which a part or the whole of the structure of the power generation system is replaced with its alternative structure. For example, a fuel cell apparatus is structured as the power generation system, and the whole of the fuel cell apparatus in which a fuel cell stack and a fuel tank are integrally connected to each other can be made detachable from a casing of the electronic equipment.
Alternatively, the fuel cell stack may be incorporated into the casing side of the electronic equipment so that only the fuel tank is detachable from the casing of the electronic equipment.
Further, according to the following embodiments, a description will be made of structural examples in which oxygen in an atmosphere is taken in to be utilized as an oxidizer. However, as the oxidizer, another gaseous or liquid substance exerting an oxidative effect corresponding to oxygen may be used.
Further, in a case where oxygen is used as the oxidizer, instead of taking in the oxygen from the atmosphere, the oxygen may be supplied from an oxygen gas cylinder or an oxygen gas generation device by connecting the oxygen gas cylinder or the oxygen gas generation device to the fuel cell stack.
Further, a description will be made of an example in which the present invention is applied to a fuel cell of a polymer electrolyte type using a hydrogen gas. However, the fuel cell is not limited to this type. With a fuel cell using another fuel (for example, methanol) or a fuel cell of another type (for example, a solid oxide type or a phosphoric acid type), the same effect can be obtained.
Further, as long as the power generation system performs power generation by receiving supply of a fuel, the power generation system is not limited to the fuel cell. For example, the power generation system may be a power generation system with a micro engine utilizing a microturbine, which is formed by using a MEMS technology.
In the following, embodiments of the present invention will be described further in detail with reference to the drawings.
In Embodiment 1 of the present invention, a description will be made of a fuel cell apparatus to which a fuel cell system according to the present invention is applied.
In
There are provided a joint 7, a plug 7a, a socket 7b, a normally closed valve (NC valve) 8, an electronic equipment 11, and an air hole 13. Note that, also in
The fuel cell apparatus 1 according to this embodiment has a structure as illustrated in
With this connection in series, the single fuel path 29 can be used for both the first fuel cell 2a and the second fuel cell 2b. Therefore, downsizing of the fuel cell apparatus as a whole is enabled.
Further, as illustrated in
The casing of the electronic equipment 11 is provided with the air hole 13 for supplying an oxidizer (oxygen in the atmosphere) to the fuel cell apparatus 1.
Further, the first fuel cell 2a and the second fuel cell 2b each include the fuel cell unit 3 for taking out a current by electrochemically reacting a hydrogen gas and oxygen with each other.
The fuel cell unit 3 includes, as illustrated in
The diffusion layers 27 for supplying the hydrogen gas to the fuel cell units 3 are joined in the fuel path 29. The fuel path 29 communicates with the fuel tank 6.
The diffusion layer 27 is made of a porous conductive material having air permeability, allows a hydrogen gas molecule to diffuse and permeate into an entire surface of a fuel electrode 22 of the MEA 24, and serves as a current path which allows electrons of the fuel electrode 22 to escape to an electrode 25 to take out the electrons.
The diffusion layer 28 is also made of a porous conductive material having air permeability, allows oxygen gas molecules to diffuse and permeate into an entire surface of an oxidizer electrode 23 of the MEA 24, and serves as a current path which supplies electrons to the oxidizer electrode 23 from an outside.
The MEA 24 has a structure in which a polymer electrolyte membrane 21 is sandwiched between the fuel electrode 22 and the oxidizer electrode 23.
The fuel electrode 22 is an air permeable thin film layer, in which a platinum catalyst is diffused, ionizes the hydrogen gas by decomposing the hydrogen gas into hydrogen atoms, and feeds hydrogen ions to the polymer electrolyte membrane 21.
The oxidizer electrode 23 is an air permeable thin film layer, in which a platinum catalyst is diffused, and generates water molecules by reacting the oxygen gas with the hydrogen ions received from the polymer electrolyte membrane 21.
The polymer electrolyte membrane 21 allows the hydrogen ions received from the fuel electrode 22 to move therethrough to deliver the hydrogen ions to the oxidizer electrode 23 and prevents direct movement of the electrons between the fuel electrode 22 and the oxidizer electrode 23.
Accordingly, the hydrogen gas, that is, the fuel stored in the fuel tank 6 (
On the other hand, to the oxidizer electrode 23, oxygen in the atmosphere taken in through the air hole 13 (
As illustrated in
The hydrogen ions pass through the polymer electrolyte membrane 21. On the other hand, oxygen taken in from the atmosphere passes through the diffusion layer 28 to permeate into the oxidizer electrode 23. Under presence of catalyst atoms included in the oxidizer electrode 23, the oxygen is bound with the hydrogen ions which have passed through the polymer electrolyte membrane 21, thereby generating water molecules.
As illustrated in
As a result, in the external electric circuit, current corresponding to an electrochemical energy difference between the hydrogen gas and the water is taken out.
Next, a description will be made of the first fuel cell according to this embodiment.
The first fuel cell 2a includes the fuel cell unit 3 as described above.
When the fuel tank 6 is connected to the fuel cell apparatus 1 by the joint 7, the hydrogen gas in the fuel tank 6 is supplied to the fuel electrode 22 through the joint 7 after passing through the diffusion layer 27 (
On the other hand, air as the oxidizer is supplied to the diffusion layer 28 (
In this case, the first fuel cell 2a is desirably placed in the same environment as that in which the second fuel cell 2b is placed.
Next, a description will be made of the NC valve according to this embodiment.
Between the first fuel cell 2a and the second fuel cell 2b, the fuel path 29 is in a connected state by the NC valve 8. The NC valve 8 is always closed in a state where electric power is not supplied. In a state where the NC valve 8 is closed, a flow path of the hydrogen gas to the second fuel cell 2b is shut off. The first fuel cell 2a performs power generation and supplies a predetermined electric power to the NC valve 8, thereby opening the NC valve 8 to allow the hydrogen gas to be supplied to the second fuel cell 2b. In this case, in order to achieve a structure in which the first fuel cell 2a is directly connected to the NC valve 8 without an intermediation of a special control device, a value of the electric power of the first fuel cell 2a by which the NC valve 8 is opened is set to be equal to or larger than a predetermined threshold value of the first fuel cell 2a.
In setting the threshold value, a lower limit value of the electric power, which is supplied by the second fuel cell 2b and by which the electronic equipment 11 can be stably driven, is set to be equal to or larger than a value which has been converted for the first fuel cell 2a.
Specifically, in this embodiment, the first fuel cell 2a and the second fuel cell 2b include the fuel cell unit(s) 3 of the same structure, respectively. There are used the single fuel cell unit 3 for the first fuel cell 2a and the four fuel cell units 3 for the second fuel cells 2b, the four fuel cell units 3 being stacked on each other. Thus, a voltage value of the fuel cell 2a is ¼ that of the fuel cell 2b. A value of ¼ the lower limit value of the electric power, by which the electronic equipment 11 can be stably driven, is set to a threshold value of the NC valve 8.
Further, as the NC valve 8, a piezoelectric element valve or the like of a solenoid type or bimorph type is used.
Next, a description will be made of the second fuel cell according to this embodiment.
As illustrated in
When hydrogen is consumed by the second fuel cell 2b, the hydrogen gas in the fuel tank 6 is supplied to the fuel electrode 22 (
Air as the oxidizer is supplied to the diffusion layer 28 of each of the fuel cell units 3 through the air hole 13. The binding reaction between hydrogen ions and oxygen occurs, and electric power is supplied to the electronic equipment 11 electrically connected to the fuel cells 3.
Next, a description will be made of an actuation operation in the fuel cell apparatus according to this embodiment.
In a state where the fuel gas is not supplied to the first fuel cell 2a of the fuel cell apparatus 1, the NC valve 8 is in a closed state (Step F101).
Next, when the supply of the fuel gas from the fuel tank 6 is started (Step F102), the fuel gas is supplied to the first fuel cell 2a to start power generation (Step F103).
Next, in Step F104, when an output of the first fuel cell 2a is equal to or larger than a predetermined threshold value, the NC valve 8 is opened and the fuel gas is supplied to the second fuel cell 2b (Step F105) to allow the second fuel cell 2b to start power generation (Step F106).
The fuel cell apparatus 1 is then actuated (Step F107), and electric power is supplied to the electronic equipment 11.
On the other hand, when the fuel cell apparatus 1 is in an abnormal condition such as abnormal environment or the like and the output of the first fuel cell 2a is lower than the predetermined threshold value in Step F104, the NC valve 8 maintains the closed state (Step F108).
As a result, the fuel gas is not supplied to the second fuel cell 2b, so electric power is not supplied to the electronic equipment 11.
In this case, abnormality warning is issued to alert a user (Step F109), and actuation of the fuel cell apparatus 1 is stopped (Step F110).
Next, a description will be made of a stopping operation when abnormality occurs in the fuel cell apparatus according to this embodiment.
In
When, in Step G103, the output is maintained to be equal to or larger than the predetermined threshold value, the open state of the NC valve 8 is continued (Step G104).
The fuel gas is kept supplied to the second fuel cell 2b, and the power generation of the second fuel cell 2b is continued to supply electric power to the electronic equipment 11 (Step G105).
In a case where an operation of the user moves to the power off operation of the electronic equipment 11 or a standby mode (Step G106), a termination signal is input to the fuel cell apparatus 1, and the operation then moves to a termination mode.
In the termination mode, the fuel supply from the fuel tank 6 is stopped (Step G107), and the fuel cell apparatus 1 is stopped (Step G108).
On the other hand, when the fuel cell apparatus 1 is in an abnormal condition such as abnormal environment or the like and the output of the first fuel cell 2a is lower than the predetermined threshold value in Step G103, even in a case where there is no fuel cell termination command (Step G106), the NC valve 8 is closed (Step G109).
The fuel supply to the second fuel cell 2b is then stopped.
As a result, the power generation of the second fuel cell 2b is stopped (Step G110), the abnormality warning is issued to alert the user (Step G111), and the fuel cell apparatus 1 is stopped (Step G112).
As described above, electric power is supplied by the power generation of the first fuel cell 2a, with the result that opening and closing of the valve for supplying a fuel to the second fuel cell 2b to drive the electronic equipment are performed without using special electric power supply unit such as a secondary battery.
Thus, there can be provided a fuel cell apparatus which has a simple system structure, which can be downsized, and which can be incorporated in a small electronic equipment.
Further, in a case where the fuel cell apparatus 1 is in the abnormal environment and the output of the first fuel cell 2a is abnormally reduced, the NC valve 8 is automatically closed, so the fuel supply to the second fuel cell 2b is stopped.
Accordingly, a fail safe mechanism of a passive type is realized, so the fuel cell apparatus with higher stability can be provided.
The description has been made while the first fuel cell 2a includes the fuel cell unit 3 of the fuel cell. However, the first fuel cell 2a may include a plurality of fuel cell units 3 stacked on each other to constitute a stacked structure.
Further, any apparatus may be used as long as the power generation is performed by using a fuel, and the catalyst combustor using a catalyst may be used.
In the structural example, the one first fuel cell 2a and the one second fuel cell 2b are arranged. However, as long as desired functions and output can be obtained, each of the first fuel cell 2a and the second fuel cell 2b may be obtained by electrically connecting a plurality of stacks.
In Embodiment 2 of the present invention, a description will be made of a structural example in which a first fuel cell is used as an environment sensor.
In this embodiment, the first fuel cell 2a is used as the environment sensor by using change in environmental characteristics of the fuel cell.
As a result, stability against environmental variation can be improved.
As characteristics of the fuel cell, a dry-out phenomenon in which a moisture content in the fuel cell unit is insufficient at high temperature occurs.
Further, as moisture characteristics, when a humidity is low, a membrane resistance of the polymer electrolyte membrane 21 increases, thereby deteriorating performance thereof.
In the abnormal environment, as illustrated in a graph of I-V characteristics of
In the above-mentioned low humidity or high temperature state, as illustrated in
By utilizing the above-mentioned characteristics, the predetermined threshold value of a voltage for opening the NC valve 8 is set between the line corresponding to the normal environment (solid line) and the line corresponding to the abnormal environment (broken line).
As a result, there can be achieved a structure in which, in abnormally high temperature condition or abnormally low humidity condition, the NC valve 8 is closed, and the fuel supply of the second fuel cell 2b is stopped. Thus, the fuel cell apparatus 1 can be increased in stability against the abnormal environment.
In Embodiment 3 of the present invention, a description will be made of a structural example in which the first fuel cell and the second fuel cell are connected to the fuel path in parallel to each other.
In Embodiment 1 of the present invention, the first fuel cell 2a and the second fuel cell 2b are connected to each other by the fuel path 29 in series, the fuel path 29 being in the connected state by the NC valve 8.
This embodiment employs a structure in which, as illustrated in
Even with this structure, the same effect as that of Embodiment 1 of the present invention can be obtained.
In this case, by branching the fuel path 29, the second fuel cell 2b can be separated from a supplied gas. Therefore, a pressure or a flow rate of the fuel gas can be adjusted for the first fuel cell 2a.
A smaller amount of the fuel for allowing the first fuel cell 2a to perform power generation is sufficient than that for the second fuel cell 2b. Thus, there is no need for the first fuel cell 2a and the flow path there around to deal with a high voltage and a high flow rate as compared to the serial connection, so the first fuel cell 2a can be simplified, and the downsizing is possible.
Further, a degree of freedom of fuel path arrangement for the first fuel cell 2a is high, so a degree of freedom of a layout design of the fuel cell can be increased.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2006-271462, filed Oct. 3, 2006, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-271462 | Oct 2006 | JP | national |
